A plasma display panel (hereinafter abbreviated as a PDP or a panel) is a display device having excellent visibility and featuring a large screen, thinness and light weight. The systems of discharging a PDP include an alternating current (AC) type and direct-current (DC) type. The electrode structures thereof include a three-electrode surface-discharge type and an opposite-discharge type. However, the current mainstream is an AC type three-electrode PDP, which is an AC surface-discharge type, because this type of PDP is suitable for higher definition and easy to manufacture.
Generally, an AC type three-electrode PDP has a large number of discharge cells formed between a front panel and a rear panel facing each other. In the front panel, a plurality of display electrodes, each made of a pair of a scan electrode and a sustain electrode, are formed on a front glass substrate in parallel with each other. A dielectric layer and a protective layer are formed to cover these display electrodes. In the rear panel, a plurality of parallel data electrodes is formed on a rear glass substrate. A dielectric layer is formed on the data electrodes to cover them. Further, a plurality of barrier ribs is formed on the dielectric layer in parallel with the data electrodes. Phosphor layers are formed on the surface of the dielectric layer and the side faces of the barrier ribs. Then, the front panel and the rear panel are facing each other and sealed together so that the display electrodes and data electrodes intersect with each other. A discharge gas is filled into an inside discharge space formed therebetween. In a panel structured as above, ultraviolet light is generated by gas discharge in each discharge cell. This ultraviolet light excites respective phosphors to emit R, G, or B color, for color display.
A general method of driving a panel is a so-called sub-field method in which one field period is divided into a plurality of sub-fields and a combination of light-emitting sub-fields provides gradation images for display. Each of the sub-fields has an initializing period, writing period, and sustaining period.
In the initializing period, all the discharge cells perform an initializing discharge operation at a time to erase the history of wall electric charge previously formed in respective discharge cells and form wall electric charge necessary for the subsequent writing operation. Additionally, this initializing discharge operation serves to generate priming (priming for discharge=excited particles) for causing stable writing discharge.
In the writing period, scan pulses are sequentially applied to scan electrodes, and write pulses corresponding to the signals of an image to be displayed are applied to data electrodes. Thus, selective writing discharge is caused between scan electrodes and corresponding data electrodes for selective formation of wall electric charge.
In the subsequent sustaining period, a predetermined number of sustain pulses are applied between scan electrodes and corresponding sustain electrodes. Then, the discharge cells in which the wall electric charge are formed by the writing discharge are selectively discharged and light is emitted from the discharge cells.
In this manner, to properly display an image, selective writing discharge must securely be performed in the writing period. However, there are many factors in increasing discharge delay in the writing discharge, such as: restraints of the circuitry inhibit the use of high voltage for write pulses; and phosphor layers formed on the data electrodes make discharge difficult. For these reasons, priming for generating stable writing discharge is extremely important.
However, the priming caused by discharge rapidly decreases as time elapses. This causes the following problems in the method of driving a panel described above. In writing discharge occurring a long time after the initializing discharge, priming generated in the initializing discharge is insufficient. This insufficient priming causes a large discharge delay and an unstable writing operation, thus degrading the image display quality. Additionally, when a long writing period is set for a stable writing operation, the time taken for the writing period is too long.
Proposed to address these problems are a panel and method of driving the panel in which auxiliary discharge electrodes are provided and discharge delay is minimized using priming caused by an auxiliary discharge (see Japanese Patent Unexamined Publication No. 2002-297091, for example).
However, such panels have the following problems. Because the discharge delay of the auxiliary discharge itself is large, the discharge delay of the writing discharge cannot sufficiently be shortened. Additionally, because the operating margin of the auxiliary discharge is small, incorrect discharge may be induced in some panels.
Further, when the number of scan electrodes is increased for higher definition without shortening the discharge delay in the writing discharge sufficiently, the time taken for the writing period is too long and the time taken for the sustaining period is insufficient. As a result, luminance decreases. Additionally, increasing the partial pressure of xenon to increase the luminance and efficiency further increases the discharge delay and makes the writing operation unstable.
The present invention addresses these problems and aims to provide a method of driving a plasma display panel capable of performing stable and high-speed writing operation.